Three projects will be pursued. I. Futile Cycles in Glucose Metabolism in Liver Cells. Recycling between glucose and glucose 6-P and fructose 6-P and fructose 1,6 P2 will be studied with the use of tritium labeled glucose. Methods to quantitate this cycling have been derived. They require the isolation of glucose 6-P, fructose 6-P and fructose 1,6 P2 formed in liver from tritium labeled glucoses and estimation of their specific activities. Procedures for this technique will be developed and the recycle determined under a variety of conditions. II. Methods to estimate the oxidation of glucose 6-P via the pentose cycle in liver during glucose synthesis will be developed and tested. The role of the pentose cycle in providing TPNH for fatty acid synthesis will be studied. III. Glycogen Synthesis in Hepatic Rat. The role of insulin and adrenal corticoids in glycogen synthesis by isolated rat hepatocytes will be studied. BIBLIOGRAPHIC REFERENCE: Glycogen synthesis by a strain of Enrlich ascites tumor. J. Katz, S. Golden, D. Rubinstein and R. Van der Velde. Biochem. Biophys. Res. Comm. 63, 269-277, 1975.